Seismic visibility of eclogite in the Earth’s upper mantle – implications from high pressure-temperature single-crystal elastic properties of omphacite

Authors

Ming Hao, University of New MexicoFollow
Jin S. Zhang, University of New MexicoFollow
Wen-Yi Zhou, University of New Mexico
Qin Wang, Nanjing University, China

Publication Date

2020

Document Type

Dataset

Abstract

Eclogite, constituting the subducted crust, is one of the most important geochemical and geophysical heterogeneities in the Earth’s mantle. As the dominant anisotropic phase in eclogite, precise high pressure-temperature single-crystal elastic properties of omphacite provides the basis for detecting eclogite in the Earth’s upper mantle. In this study, we measured the single-crystal elastic moduli of omphacite up to 18 GPa and 700 K using Brillouin spectroscopy. A least-squares fit to a third-order finite strain equation of state yields K_S0’=4.5(1), G₀’=1.53(5), ∂K_S0/∂T=-0.029(5) GPa/K, ∂G₀/∂T=-0.013(5) GPa/K, with ρ₀=3.34(1) g/cm³, K_S0=123(3) GPa, and G₀=74(2) GPa. We found that the seismic velocities of eclogite are similar to pyrolite at the depths of 200-300 and 410-500 km, thus eclogite is seismically invisible at these depths. Combined with the lattice-preferred orientations of the omphacite in naturally deformed eclogites, we also modeled seismic anisotropy of eclogite at various pressure-temperature conditions.

Recommended Citation

Hao, Ming; Jin S. Zhang; Wen-Yi Zhou; and Qin Wang. "Seismic visibility of eclogite in the Earth’s upper mantle – implications from high pressure-temperature single-crystal elastic properties of omphacite." (2020). https://digitalrepository.unm.edu/eps_fsp/10